Inkjet printing, widely employed in copiers, printers, facsimile machines, and so forth for home and office use, has, as a result of improvement in print quality in recent years, also come to be utilized for catalogs, magazines, packaging labels, and other such paper items; cans and other such metal products; tiles and other such ceramic products; film and other such resin products; fabric and other such textile products; and other such examples of commercial and/or industrial printing. In such various types of printing, various dyes are employed in correspondence to the type of substrate material that is to be imparted with coloration. For example, disperse dyes and other such water-insoluble dyes are employed when carrying out printing on textile products such as fabrics made of hydrophobic fibers or the like. Known as methods of use of such water-insoluble dyes to carry out printing on fabrics made of hydrophobic fibers are textile printing in which ink is directly applied to fibers, following which steaming or other such heat treatment is employed for fixing of dyes; and textile printing carried out by means of sublimation thermal transfer in which ink is applied to paper or other such intermediate recording medium, following which fibers are brought into contact with the intermediate recording medium, and heat is used to cause dye to be sublimated and transferred from the intermediate recording medium to the fibers (see, for example, Patent Literature 1).
Because the inks employed in textile printing using such water-insoluble dyes generally employ water as solvent, it is necessary to disperse the water-insoluble dyes in water. This being the case, dispersants are generally employed. But because of such issues as the fact that particles in ink that contain the water-insoluble dyes may flocculate and precipitate during or after preparation thereof, dispersion stability during preparation and/or during storage has not always necessarily been satisfactory. Furthermore, because stability during storage is not satisfactory, in the case of an inkjet printer there has also been the problem that stability during jetting has not been satisfactory.
Patent Literature 1 discloses an anthraquinone derivative, though it should be noted that this is disclosed as a dispersant for pigment used in connection with color filters. However, what is disclosed at Patent Literature 1 is little more than particle diameter when pigment for use in color filters is dispersed in a hydrophobic organic solvent and the effect of this on color filter contrast.